1. Field of the Invention
The present invention relates to fiber optic cables used for indoor and/or outdoor applications and, in particular, to fiber optic cables having an improved buffer region and with improved performance characteristics.
2. Description of the Related Art
In the wiring of premises, such as apartment and commercial buildings, with fiber optic cables, it is common to use a cabling system in which many cables enter the premises and individual cables are broken out for use in individual stations within the building. Heretofore, it has been known to use a high density breakout cable system for wiring such premises. Typically, the fiber optic cables of such a cable system (known as xe2x80x9cbreakout cablesxe2x80x9d) are available in spools which can be pulled through the building in a routine manner.
Typically, the prior art breakout cables are constructed with water blocking properties such as by incorporating greases and/or gels between an outer jacket and internally carried fibers of the cables. The greases and/or gels are intended to prevent water from migrating through and about the fibers of the cable if the outer jacket of the cable becomes breached in some manner. Although meeting with a certain degree of success, cables incorporating the prior art greases and gels can be difficult to work with due to the messiness and handling difficulties thereof. For example, the greases and/or gels can tend to leak from the cable, such as during a cable termination process. Additionally, the greases and/or gels are particularly undesirable when exposed to warm temperatures because the warmed greases and/or gels tend to flow more readily within the cable jacket and can tend to drip out of the cable, such as at a cable termination point, thereby potentially soiling or damaging components, including electrical and/or electronic components, found within a cable termination cabinet as well as diminishing the water blocking properties of the cable. Furthermore, many prior art cables incorporate a buffer material surrounding the fibers that are difficult or require specialized tools to strip from the fiber for splicing and termination purposes. Also, as fiber sensitivity continues to increase to accommodate greater bandwidth, prior art buffer material may result in unacceptable attenuation of these fibers when tested under standards for fiber optic indoor/outdoor cable as developed by the Insulated Cable Engineers Association, Inc., for example ICEA-696.
Finally, many prior art cables allow an unacceptable amount of the weight of the cable, and any load applied to the cable such as by wind, snow, and/or ice, to be carried by the optical fibers which may damage destroy or shorten the life of the cable.
Therefore, there is a need to provide improved fiber optic cables that address these and other shortcomings of the prior art.
Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The present invention generally is directed to dry core indoor/outdoor fiber optic cables which do not incorporate greases and/or gels for water blocking and that have an improved buffer region and improved performance characteristics. In a preferred embodiment, the cable incorporates a plurality of sub-units with each of said sub-units being arranged adjacent another of the sub-units so that the plurality of sub-units define an outer periphery. Preferably, each of the sub-units includes a plurality of optical fibers at a first tension and a first lay length that at least partially surround a central strength member, a buffer material surrounding each individual optical fiber, a strength member layer at a second tension and a second lay length, and a sub-unit jacket, with each of the optical fibers being arranged adjacent another of the optical fibers. The sub-unit jacket surrounds the optical fibers, with the strength member layer being disposed between the optical fibers and the sub-unit jacket and the optical fibers disposed between the strength member layer and the central strength member. An outer jacket surrounds the plurality of sub-units, with water blocking tape being disposed between the outer jacket and the outer periphery of the sub-units. The buffer material possesses properties such that the attenuation of the optical fibers is reduced as compared to prior art buffer materials, the cable is able to meet ICEA-696 standards, and the buffer material is easily strippable from the optical fibers for ease of terminations and splices.
In accordance with another aspect of the present invention, the cable incorporates an elongated organizer which possesses a first breaking strength. At least one water blocking yarn member is arranged about the organizer and a plurality of sub-units are arranged in reverse-oscillated lay about the organizer so that the water blocking yarn member is disposed between the organizer and the plurality of sub-units. Preferably, each of said sub-units include a plurality of optical fibers at a first tension and a first lay length, a buffer material surrounding each individual optical fiber, a strength member layer at a second tension and a second lay length, and a sub-unit jacket. The strength member layer possesses a second breaking strength, each of the optical fibers possess a third breaking strength, with the first breaking strength being greater than the second breaking strength and the second breaking strength being greater than the third breaking strength. The buffer material possesses properties such that the attenuation of the optical fibers is reduced as compared to prior art buffer materials, the cable is able to meet ICEA-696 standards, and the buffer material is easily strippable from the optical fibers for ease of terminations and splices.
In accordance with yet another aspect of the present invention, an alternative embodiment of the cable includes a plurality of optical fibers, a buffer material surrounding each individual optical fiber with the buffered optical fibers having a first tension and a first lay length that at least partially surround a central strength member, a strength member layer having a second tension and a second lay length, and an outer jacket, with each of the optical fibers being arranged adjacent another of the optical fibers. The outer jacket surrounds the optical fibers, with the strength member layer being disposed between the optical fibers and the outer jacket and the buffered optical fibers disposed between the strength member layer and the central strength member. The strength member layer possesses a first breaking strength, each of the buffered optical fibers possess a second breaking strength, with the first breaking strength being greater than the second breaking strength. The buffer material possesses properties such that the attenuation of the optical fibers is reduced as compared to prior art buffer materials, the cable is able to meet ICEA-696 standards, and the buffer material is easily strippable from the optical fibers for ease of terminations and splices.
In accordance with yet another aspect of the present invention, an alternative embodiment of an indoor/outdoor dry core fiber optic cable assembly includes a plurality of optical fibers, a buffer material surrounding each of the individual optical fibers and the buffered optical fibers having a first tension and a first lay length that at least partially surround a central strength member, a strength member layer having a second tension and a second lay length, and an outer cover, with each of the optical fibers being arranged adjacent another of the optical fibers. The outer cover surrounds the optical fibers and may be a sub-unit jacket or an outer jacket, with the strength member layer being disposed between the optical fibers and the outer cover and the optical fibers disposed between the strength member layer and the central strength member. The strength member layer possesses a first breaking strength, each of the buffered optical fibers possess a second breaking strength, with the first breaking strength being greater than the second breaking strength. The buffer material possesses properties such that the attenuation of the optical fibers is reduced as compared to prior art buffer materials, the cable is able to meet ICEA-696 standards, and the buffer material is easily strippable from the optical fibers for ease of terminations and splices.
The numerous features and advantages of the present invention will be more readily apparent from the following detailed description read in conjunction with the accompanying drawings.